The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to processes for the preparation of toners with improved wax dispersion and wherein in embodiments the use of compatibilizers can be avoided. In embodiments the process of the present invention is directed to the preparation of a master batch of wax and flow aid additives, such as silica particles, by the premixing of the wax and silica, and thereafter adding the resulting mixture to resin particles and pigment to enable the generation of a toner with improved wax dispersion. Also, in embodiments the toner prepared in accordance with the present invention contains, for example, less than 10 percent (by number) articles smaller than 4 microns in volume average diameter, and less toner fines after classification; thus, for example, fewer classifications are needed to obtain the desired fines content. Less toner fines results in less toner impaction onto the carriers in the developer housing, improved toner powder flow, and lower amounts of toner surface additives are needed. Improved wax dispersion obtained with the processes of the present invention was illustrated by TEM micrographs. Also, the toners of the present invention possess excellent classification efficiencies, high hot offset temperatures of, for example, between 400.degree. F. and 500.degree. F., superior melt (MFT) fusing temperatures between 200.degree. F. and 310.degree. F., and broad fusing latitudes of 90.degree. F. to 250.degree. F. Moreover, in embodiments of the present invention there are enabled toners with rapid admix of less than about 15 seconds, extended developer life, stable electrical properties, high image print quality with substantially no background deposits, and compatibility with fuser rolls including VITON.RTM. fuser rolls. The aforementioned toner compositions contain pigment particles comprised of, for example, carbon black, magnetites, or mixtures thereof, cyan, magenta, yellow, blue, green, red, or brown components, or mixtures thereof thereby providing for the development and generation of black and/or colored images. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic imaging and printing processes, including color processes.
Toners with waxes, such as low molecular weight waxes, are known as illustrated herein. Problems encountered with waxy toners are as illustrated herein and include the poor wax dispersion of the wax in the toner. Poor wax dispersion enables the wax to escape from the toner and thereby adversely effect the toner characteristics, and deposit on copying and printing machine parts. Loose wax particles are likely to be taken out by toner classification, which provides lower wax content in the final toner products and causes problems in toner fines recycling. Poor wax dispersion also provides poor toner powder flow, and the need for higher amount contents of surface additives, which can cause problems in toner RH sensitivity. Poor toner powder flow leads to lower efficiency in the toner classification processes and more time is needed to remove the toner fines. These and other problems are avoided, or minimized with the processes of the present invention.
Toners with low molecular weight waxes, such as polypropylenes and polyethylenes commercially available from Allied Chemical and Petrolite Corporation, EPOLENE N-15.TM. commercially available from Eastman Chemical Products, Inc., VISCOL 550-P.TM., a low weight average molecular weight polypropylene available from Sanyo Kasei K. K., and similar materials, are known. The commercially available polyethylenes selected have a molecular weight of from about 1,000 to about 1,500, while the commercially available polypropylenes are believed to have a molecular weight of from about 4,000 to about 7,000. Many of the polyethylene and polypropylene compositions useful in the present invention are illustrated in British Patent No. 1,442,835, the disclosure of which is totally incorporated herein by reference. The aforementioned toners are usually prepared by simply adding the wax to the components contained in the toner, followed by mixing with heat, jetting, and classification. The wax in these toners escapes and causes the problems mentioned herein. Moreover, toners with surface additives of silica, such as fumed silicas, are known.
Further, developer compositions with charge enhancing additives, which impart a positive charge to the toner resin, are known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions. There are also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica.
Also, there are disclosed in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition. Further, there is disclosed in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions with resin particles and pigment particles, and as charge enhancing additives alkyl pyridinium compounds. Additionally, other documents disclosing positively charged toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014 4,394,430, and 4,560,635 which illustrates a toner with a distearyl dimethyl ammonium methyl sulfate charge additive, These and other known charge additives can be selected for the toners and processes of the present invention.
Moreover, toner compositions with negative charge enhancing additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resin particles, pigment particles, and as a charge enhancing additive ortho-halo phenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives.
There is illustrated in U.S. Pat. No. 4,404,271, the disclosure of which is totally incorporated herein by reference, a complex system for developing electrostatic images with a toner which contains a metal complex represented by the formula in column 2, for example, and wherein ME can be chromium, cobalt or iron. Additionally, other patents disclosing various metal containing azo dyestuff structures wherein the metal is chromium or cobalt include U.S. Pat. Nos. 2,891,939; 2,871,233; 2,891,938; 2,933,489; 4,053,462 and 4,314,937. Also, in U.S. Pat. No. 4,433,040, the disclosure of which is totally incorporated herein by reference, there are illustrated toner compositions with chromium and cobalt complexes of azo dyes as negative charge enhancing additives.